(1) Field of the Invention
The present invention relates to electrical equipment wiring trough systems used with relay panel or rack installations and the like, and in particular relates to a wiring trough system permitting easy installation of intra-panel and inter-panel wiring conductors or cables used to interconnect electrical equipment mounted in the various relay panels of the installation, and readily permits removal or replacement of a single panel within the installation.
(2) Description of the Prior Art
Industries and utilities commonly require large installations of electrical and electronic monitoring and switching equipment to enable them to provide their particular services to their customers. Such installations commonly include floor mounted panels or racks, each containing various electrical equipment which is electrically interconnected by wiring conductors and cables to various other electrical equipment contained in the same or other panels to provide the desired services. Further, limitations imposed by the space available for an installation, and the desirability of reducing point-to-point conductor lengths, have led to a standard practice of installing the panels in juxtaposed groups called switchboards, with the switchboards being arranged in parallel, back-to-back groups.
In electric utilities in particular, multi-conductor cables connect equipment located in a substation yard with an equipment panel. Normally, the conductors within the cables are terminated on a terminal block located at the lower extremity of the panel. Due to the electrical power involved, large, single conductors and generally used in point-to-point connections both within an individual panel and via wiring troughs within parallel switchboards.
In the prior art, various methods have been used to provide wiring troughs to carry the interconnecting conductors and cables, both for one switchboard and between parallel switchboards. These wiring cable troughs are utilized to maintain the conductors or cables in an orderly, out-of-the-way fashion and to support the interconnecting conductors, which may be quite heavy.
Generally, the cable troughs disclosed in the prior art are so designed and interconnected as to require that the interconnecting conductors connected into the panel installation, be pulled through the cable troughs and past the panels within the installation. The conductors to be interconnected into a particular panel must be pulled out of the trough and then threaded through the panel structure to the various electrical equipment, or to terminal boards on the panel. Pulling the conductors into the cable troughs requires many installation man-hours, the number of which increase as the number of conductors being pulled into the trough increases. This increase is due to several factors. First, pulling a large number of conductors obviously requires more time than pulling a small number. Second, each additional conductor pulled into a trough reduces the cross-sectional area within which to pull additional conductors, thereby increasing the time required to pull in the succeeding conductors. Third, the conductors must be carefully pulled through the troughs to avoid damage to the conductors and insulation, and as the number of conductors in a trough increases, the care required increases and the time required to pull the conductors correspondingly increases.
Once the conductors are positioned and interconnected, the prior art troughs are fixed in position in permanent attachment to the rear of the panels or racks. Thus if a particular panel within a switchboard is to be removed, the intrapanel conductors must be disconnected and then the interconnecting conductors must be pulled out of the panel. Next, removal of the single panel may necessitate the removal of conductors from the trough which are not associated with the particular panel being removed. Additionally, as one cable trough will carry conductors which terminate in various panels, the conductors in panels not being removed may have to be disconnected and removed from the cable trough to allow panel removal.
Conventionally, parallel installations of equipment panels or switchboards are interconnected by cross-braces attached at the upper extremity of the panels. In the prior art, these braces have provided for carrying cables between the parallel switchboard groups. For the same reasons above-described, replacing a single panel in one of the parallel groups may necessitate pulling the cable from a cross-brace. Additionally, most prior art systems require that the cross-brace be completely detached at one end, from not only the panel being removed, but also from adjacent panels on the switchboard, in order to remove the single panel from the installation. Further, to prevent damage to the still connected end of the cross-brace, all cables should be removed from the cross-brace and the unconnected end supported until a new panel is in place.
To overcome the obvious disadvantages in the above-described prior art, there is depicted and described in U.S. Pat. No. 2,567,740, an embodiment of a cable trough system having a single, open, cable trough transversely interconnected to the channel cross-bracing at a central location between the two parallel groups. However, to effect removal of a single panel, the conductors interconnected to that panel and which are carried from the central trough internally in the cross-bracing may have to be pulled. Additionally, the cross-braces must be disconnected from the panel being pulled to allow its removal, thus allowing the weight of the cables carried within the trough to cause the trough to sag and thereby risking trough damage.
It is also a common practice in the prior art to provide at least one completely enclosed, vertically-oriented, internal recess or channel within each equipment panel to receive the incoming conductors associated with the equipment supported by the panel, with such channel having openings at preselected locations to permit pulling the conductors from within the channel to the particular location of a piece of equipment with which it is to be interconnected. In such prior art panels, during installation of the panel, the conductors associated with that panel must be pulled through the vertical recess or channel and out through the preselected openings as above-described. Again, removal of a single panel from an installation will require that the conductors be completely withdrawn from the vertical recess or channel.
The disadvantages of the prior art are overcome with the present invention, and an equipment panel switchboard construction and interconnecting wiring trough system is provided which allows removal of a single panel without completely disconnecting the cross-bracing interconnecting the parallel switchboards of the installation, and which provides adequate support for the wiring subsequent to panel removal and prior to the installation of a replacement panel. Further, the present invention permits the replacement panel to be completely wired internally prior to emplacement within the switchboard group.